A long-standing problem in the area of dental and medical wrenches and, more particularly, in the area of dental torque ratchet wrenches, has been that of assuring that excessive force or torque, or less than what is specified is not advertently applied to an implant or abutment employed in a dental implant procedure. The same concern, relative to limiting of torque transmitted to a work object, exists in other areas involving delicate mechanical assembly in orthodontics and maxillofacial surgery.
In addition to the long standing need in the prior art for a torque-limiting dental and medical wrench has been the fact that, to the extent of their existence in the prior art, such wrenches have been digital in nature, that is, limit the torque that can only be controlled, i.e., one wrench, one torque setting. Accordingly, if the safest or most desirable maximum torque in a given application falls between one of the digital or incremental levels at which such a torque wrench can be set, a decision then must be made as to whether to operate the tool at a torque shear either below or above the level at which the dentist or technician would have desired.
A further problem, addressed by the present invention, is that of providing a dental torque or ratchet wrench having a sufficiently low profile to be comfortably used within the very close clinical spaces which are available in implant procedures in the mouth or in the body in orthopedic applications.
The prior art, as known to the within inventors, is represented by U.S. Pat. No. 5,129,823 (1992) to Hughes, entitled Driver Tool and Method for Implant Dentistry; and U.S. Pat. No. 5,366,412 (1994) to Beaty, et al, entitled Torque Limiting Clutch and its Uses. Further, the Dentsply Corporation is believed to offer and sell a low profile dental torque ratchet wrench. The Dentsply product is, however, not an analog system but, rather, is one, which employs a mechanical fuse to disable the driver head of the tool when a preset force is imparted thereto.
The inventors are also aware of other prior art which, particularly, included U.S. Pat. No. 2,512,032 (1950) to Mellert, entitled Yielding Torque Indicating Tool; U.S. Pat. No. 3,018,677 (1962) to Mutulo, entitled Cartridge-Type Spring Bias Means for Predetermined Torque Release Wrench; and U.S. Pat. No. 5,152,200 (1992) to Kaplan, entitled Torque Signaling Wrench. The instant system of the inventors differs from this art in a number of material ways, including the capacity of the present wrench to be readily re-calibrated by the clinician at chairside to accommodate implant placement, restorative requirements (10-20 newton-centimeters) and abutment placement (30-40 newton-centimeters). For example, said reference to Mellert is capable of only limited calibration and cannot be calibrated to the range of 20 to 40 newton-centimeters which is the range within which most implant dentistry occurs.
The reference to Mutulo does not employ a ball bearing as the means of defining the shear point of the system. Also Mutulo cannot be recalibrated and does not provide a complete shear or off axis break. As such, Mutulo cannot be utilized in any dental application.
The within inventive wrench provides for a range of calibration of between 10 and 70 Newton centimeters with formal settings provided at 10, 20, 30, 70 or specified newton-centimeters. Also, the instant wrench will break either to the left or right, a consideration of importance to a left handed dentist and where implant work is being done upon the upper teeth.
The instant improved Adjustable Analog Dental Torque Wrench differs, inter alia, from the above referenced art in that the location of the break or shear point is external to the mouth of the patient, the extent of off-axis shear so achievable is much greater than that in any prior art, and the symmetry of such shear point may be either to the left or right of the axis thereby rendering the present wrench useful to a dentist who is either left or right handed.
With respect to this latter feature, a wrench which is bi-directionally torque limiting which is not the case in any art of record. For example, U.S. Pat. No. 5,337,638, to Cos teaches a uni-directional torque-limiting wrench in which, as well, the break of the handle relative to the wrench head will occur in or near to the mouth of the patient. Such would constitute a hazardous factor if the wrench of Cos were used in such a clinical context.
The same is the case in regard to the U.S. Pat. No. 2,972,271 to Gill in which the shear point of the device would, if used in a dental context, occur in or near the mouth of the patient. In addition, the structure of Gill does not afford a sharp definition of when a torque limit has been reached in the use of the tool.
To the knowledge of the within inventors, only said U.S. Pat. No. 5,152,200 to Kaplan teaches use of a ball bearing in a torque limit sensing means, located at or near the center of the wrench. However, the pivot point thereof, that is, the point of attachment of the wrench head to the wrench handle, is so far removed in the location of the ball bearing thereof that Kaplan, while apparently bi-directional in its shear and torque sensing, is only capable of off-axis rotation in a range of 10 to 15 degrees. This is not a sufficient rotational shear to afford adequate safety in clinical dental environment. context. Accordingly, the prior art, however viewed, does not teach a bi-directional, substantially off-axis shear, and out-of-the-mouth shear, adjustable, analog torque wrench, usable for medical and dental purposes.